I would like to thank everyone that has given me advise so far on this siteI am building a road bike from the late 80s with 126mm spacing between the dropoutsIt had a rear wheel with 7speed freewheel which wasnt the screw on type but is stuffedNow i have got another wheel off a similiar aged bike with the same rear spacing but only has a 6 speed freewheelI want to go to a bike shop today and buy a new chain and freewheel but if i buy a 7 speed freewheel do u think the offset of the wheel will be right after having a 6 soeed on it originally????I suppose what i am asking is there a difference in offset of the spoking between 6 and 7 speed wheels and if i should stick to the 6 speed thats on it ??Thans heaps for help with my dumb questions

From memory(beware! not the most reliable thing:)) the overall width of 6 and 7 speed freewheels is pretty close so you should be OK. Sheldon Brown's site has an excellent summary of these things, so I suggest checking there rather than take my word for it.

Stepr is close- Sheldon covers this somewhere and is the first place to look. In my experience, 126mm 6 and 7 speed freewheels are placed a little differently on the axle. If you put a 7 speed freewheel in place of a 6 speed, the chain will rub on the frame in the smallest gear. You need to make more space on the right side of the axle. The simplest approach (works mostly, irritating thereafter) is to add a 2pm washer on the axle loose between the lock nut and frame. Must remember it when putting the wheel back each time. It may mean your hollow axle doesn't engage in the dropout enough on the drive side. You may need to re-dish the wheel (re-centre the rim) so that it doesn't rub on the brakes. A better approach is to add the washer to the spacer between the drive side locknuts, or even find a longer spacer, or spin one up. Also re-centre the axle in the hub to have the same amount sticking out of the locknuts each side. 128mm will still fit in the frame OK. Set the RD stops whichever way you approach it.